Sheryll Barker can tell the differences between lark sparrows, field sparrows and white crown sparrows. It’s a skill in demand this time of year.

Since 1900, the National Audubon Society has held its annual bird census, the Christmas Bird Count, which is organized around so-called circles. Each circle picks a day between Dec. 14 and Jan. 5 for its 24-hour canvass of bird life in ponds, fields, woods and even supermarket parking lots.

It’s common for volunteers to participate in several counts among the seven circles in the Dallas-Fort Worth area, each of which covers a designated 15 miles in diameter.

Barker has counted in many of them since she began volunteering in 1990. This year promises to be perhaps the most satisfying. She is helping organize a new circle taking shape around the Dogwood Canyon Audubon Center in her hometown of Cedar Hill. The area hosts some prime bird habitat, including Joe Pool Lake and adjacent woods, such as the Cedar Ridge Preserve and Cedar Hill State Park.

Barker’s 3-acre yard isn’t a bad spot for birding, either, she says, noting that she’s seen two barred owls that nest in the adjacent woods.

“A childhood passion has been reignited with the birds,” Barker, 49, says. She has worked as a research scientist at UT Southwestern Medical Center but now is content to be a citizen scientist volunteering with the conservation organization.

“There has been this big amateur tradition in ornithology,” says Tania Homayoun, senior manager for conservation and education at the Dogwood Canyon Audubon Center. “Some of the most knowledgeable people are people who aren’t scientists by trade, but they know their birds really well and they can tell you where they are living.”

Counting, not shooting

Amateur bird watching began in the mid-1700s in Europe, where people kept track of when birds returned in the spring. In the United States, amateurs have been contributing information about nesting birds to government surveys since the early 1800s, she says.

The winter bird survey originated against a backdrop of humans pushing birds to the brink in the late 1800s, Homayoun explains. The craze for plumes in women’s hats led to about 5 million birds being shot each year to serve the millinery trade.

At the same time, the tradition of Christmas “side hunts” also was taking a toll on North American birds. People gathered for the holiday would pick sides, head to the outdoors, and see who could kill the most birds and animals in a given time.

Calls to protect and conserve the nation’s dwindling natural world were beginning to gain ground around that time. John Muir’s Sierra Club, for instance, formed in 1892.

Frank Chapman, an ornithologist who became an early officer in the Audubon Society after its founding in 1905, proposed counting rather than shooting birds as a preferable way to spend the yuletide holiday.

On Christmas Day 1900, 27 bird counters went out in 25 locations, mostly in the Northeast, and tallied 89 species. The count has expanded steadily since, and last year, 2,248 circles — including new additions in Latin America and the Caribbean — reported results.

The winter census, which supplements summer counts of breeding birds, lets ornithologists track bird populations and migration ranges. It has provided some stark findings. In the last 40 years, the number of purple martins has declined 78 percent, the redheaded woodpecker 89 percent and the eastern meadowlark 71 percent, according to Homayoun.

“A lot of it has to do with the way we are changing the land,” she says.

At the same time, birds that are able to coexist with humans in the cities and suburbia are increasing. In this area, that is particularly true of white wing doves, which 40 years ago were much rarer.

The count also has revealed that a number of species are remaining much farther north as climate change has raised average daily temperatures, she says. American robins, which form large flocks and migrate, would fly at least south of the Red River during winters 40 years ago. Today their winter range stretches about 200 miles farther north, Homayoun says.

“The fact is, whatever is going on, we are seeing changes in the way birds are over-wintering. This is one of the most fascinating things coming out of the Christmas count data,” she says.

Start with owling

For some counting groups, work begins before dawn with a search for owls.

Owling, as it is called, entails going to promising woodland areas and using various calls to prompt replies. North Texas is home to barred owls, screech owls, barn owls and great horned owls, all more often heard than seen by experienced birders.

Calls start with the small owls first because the entire forest is apt to go silent after the great horned owl call is sounded.

For the Cedar Hill count on Tuesday, Homayoun says, it is important to attract some experienced birders because there are areas where “you aren’t going to see a lot of backyard-type birds.”

Still, she is happy to lead novices who want to learn.

In either case, the circle needs about 25 to 30 birders to be successful, Barker explains.

For experienced birders like Barker, rare sightings are the biggest thrill. In 2006, she spotted a red-breasted grosbeak, a boldly colored migratory bird that by this time of year is found only in the tropics.

Said Homayoun, “You never know from year to year what you’re going to get.”

To join the count in Cedar Hill, or anywhere else where a National Audubon Society’s count has been organized, go to birds.audubon.org/christmas-bird-count. Participation is free.

Thomas Korosec is a Dallas freelance writer.

To participate

Dogwood Canyon Audubon Center is at 1206 W. FM1382 in Cedar Hill. Visit dogwoodcanyonaudubon.org to learn more about the center. For more details about the Christmas Bird Count in that area, scheduled for Jan. 1, contact Tania Homayoun at 469-526-1986 or thomayoun@audubon.org.

Another Christmas Bird Count in this area is being organized by the Trinity River Audubon Center, 6500 Great Trinity Forest Way (formerly 6500 S. Loop 12) in Dallas. The date for that count is Jan. 5. For more details, contact Sahar Sea, 214-309-5813 or ssea@audubon.org.

Try feeders the pros use

Interested in attracting birds to your place? Dogwood Canyon Audubon Center sells bird feeders it installs on the property in its nature shop, including these below. Specific feeders cycle in and out of the inventory.